Respect FCKConfig.ProcessHTMLEntities when FCKConfig.FillEmptyBlocks is enabled

Description

In the 2.4 version of editor/_source/internals/fckxhtml.js when FCKConfig.FillEmptyBlocks is enabled, the _AppendChildNodes function will insert &nbsp; in empty blocks. HOWEVER, when FCKConfig.ProcessHTMLEntities is false we should insert #160 instead.

The insertion of &nbsp; will generate invalid XHTML, whereas using &#160 will generate valid XHTML.

In the 2.4 version of editor/_source/internals/fckxhtml.js when FCKConfig.FillEmptyBlocks is enabled, the _AppendChildNodes function will insert &nbsp; in empty blocks. HOWEVER, when FCKConfig.ProcessHTMLEntities is false we should insert #160 instead.

Your assumption is correct, as this is the way we do to preserve subsequent white spaces.